The present invention relates to a plunger which is suitable for use in high pressure compressors, for instance, for the production of plastic materials.
The production of plastic materials is often made according to a so-called high pressure process, in which the pressure is between 1000 and 3500 bar (100-350 MPa). This fact makes particular demands upon the materials which are used in the process.
Earlier plungers of steel have been used but since it has been evident that the wear becomes very great, solid plungers of cemented carbide have been used. Cemented carbide, however, is an expensive material and has considerably higher density than steel. This means that a plunger wholly made of cemented carbide is very heavy and causes wear on moving parts in the compressor.
It is, therefore, an object of the present invention to minimize or obviate problems of this sort.
It is another object of the invention to provide a durable, light-weight plunger which is less expensive.